Happy Death Day: Time Loop Clues in First Movie Explained

Happy Death Day may spend more of its time explaining the slasher mystery than the actual science fiction behind the time loop that forms the movie, but now that the sequel is out, the director finally reveals the clues that fans missed in the first movie.

The director had previously teased that there was a true explanation for Tree Gelbman living her life over and over (and over, and over, and over) again in the first film. But not only was there an explanation behind the time travel, the film itself includes TWO major hints as to why it's happening. With the sequel Happy Death Day 2U finally revealing the explanation for Happy Death Day's time loops, the original clues can be spotted and understood.

The Power Outages in Happy Death Day Explained

Fans curious to know more about the logic and quantum pseudo-science on display as part of the sequel's plot (or who totally missed the real time loop theory at work) should read our full explainer of Happy Death Day 2U's time loops and ending. But looking specifically at the first film knowing what's REALLY taking place, the first clue is one that may have stood out to some viewers on their first watch. We're referring, of course, to the many power outages that take place across the university campus in the hours (and apparently days) leading up to Tree's murder.

It was these same power outages used by Tree to ultimately get the drop on escaped murderer John Tombs, so there's a good chance viewers made a connection that was more than mere coincidence. Having seen the second film, it's explained that the power outages are the result of Ryan's experiments with a device dubbed the Sisyphus Quantum Cooling Reactor, or "Sissy" for short. He and his fellow students built it with the intention of slowing down time, but inadvertently wound up creating the time loop in the first place.

But even more than the power outages caused by attempted firings of Sissy is the timing. Specifically the power outage caused by Sissy firing at 9:23 pm, which is used as a pivotal make-or-break plot point in both movies. In the first, it simply cut the power. Fans didn't know that it was also forming something of a Quantum bridge, or an opening that would eventually return Tree back to the moment Sissy fired in her own timeline.

As we said before, these are clearly the easier to spot of the two major clues, since it can be seen over and over, practically forcing viewers to ask what is causing them. But the second, far more brilliant clue paid off in Happy Death Day's revealed exactly what caused Tree's time loop... and it was literally the first thing that audiences heard in the opening credits.